1. Field of the Invention
This invention relates to a method for producing an edged tool, such as a cutting knife.
2. Prior Art
An edged tool provided with a surface carbide coating, such as one of vanadium carbide, is excellent in its cutting ability and its durability because of the hardness of the carbide coating.
Producing the edged tool provided with the surface carbide coating, however, requires grinding to form a cutting edge portion after forming a relatively thick carbide coating on an edged tool to be treated. However, the carbide coating is extremely hard, about 3000 Vickers hardness, and grinding therefore takes considerable time. Moreover, during grinding, portions along the edge are apt to be broken off, causing considerable inconvenience. Therefore, much labor and time must be spent to produce an edged tool.
The inventors have conducted a large number of investigations in order to produce an edged tool, which is excellent in its cutting ability and durability, without having to grind a carbide layer formed on the surface thereof. An edged tool material, made of carbon steel, has been immersed in a carbide-layer-forming bath, thus forming a dense and smooth carbide layer on the surface of an edge portion thereof. The tool material is rapidly cooled to be hardened. However, this process does not produce an edged tool having a cutting-edge portion which is excellent in its cutting ability and durability.